1. Field of Invention
This present invention relates to a paper collecting device, and more particularly to a paper collecting mechanism used in an automatic document feeder.
2. Description of Related Art
In common visual imaging output devices such as photocopying machine, fax machine, scanners or the like, image reading is accomplished by placing the original document on top of a glass platen. The optical reading unit is placed underneath the glass platen for reading the image of the original document. Due to increase usage of the automatic document feeder (herein after abbreviated as ADF) to feed original documents into the photocopying machine for images to be read, the position of the optical reading unit can be better defined and therefore reducing the area of the glass platen. The other application of the ADF is to place it on top of the glass platen. The stacked original documents are placed inside the tray of the ADF allowing the paper collecting device inside the ADF to feed the document to the glass platen for image reading. Furthermore, ADFs are applicable to printers or other machines that require paper separation.
FIG. 1 and FIG. 2 are the schematic diagrams of a conventional paper collecting device. The paper collecting device 100 has a separation roller 110, a drive roller 120, and a feed roller 130, a support member 140, and a elastic member 150 supported between top wall 20 bottom wall 30. Paper 10 feeds under the feed roller 130 in a forward direction as indicated by the arrow. Support member is seated horizontally and is connected to separation shaft 112, drive shaft 122, and feed shaft 132. When separation roller 112 rotates, it will also rotate drive roller 120, feed roller 130, and support member down around separation shaft 112 and extend elastic member 150 to press down feed rim 136 to contact the surface of paper 10, as illustrated in FIG. 2. The continuous rotation of separation gear 114 rotates drive gear 124 to turn feed gear 134 and feed rim 136, which are both mounted on feed shaft 132. As a result, feed gear 134 rotates feed rim 136 and feeds the paper forward.
Please refer to FIG. 2, when paper 10 is fed in by feed rim 136 till it is between separation rim 116 and bottom wall 30, the continuous rotating separation gear 114 engages the one-way clutch 118 to turn separation rim 116. Once the separation process of paper 10 is finished, rotating separation rim 116 will immediately reverse rotation in the other direction to operate other parts. At this moment, one-way clutch 118 activates and releases separation rim 116 from separation gear 114 to allow free rotation. This will prevent separation rim 116 from pushing paper 10 in the reverse direction and causing paper wrinkle. At the same time, elastic member 150 will retract support member 140, feed roller 130, and drive roller 120, and prevent separation 136 from pushing paper 10 in. Afterwards, separation gear 114 stops rotating and returns the paper collecting device back to the state in FIG. 1.
The disadvantage of the conventional paper collecting device in FIG. 2 is paper wrinkle and tear. When paper 10 leaves separation rim 116, separation 112 immediately reverses rotation causing one-way clutch 118 to activate and to release separation rim 116 from separation shaft 112. This prevents separation rim 116 to further push in paper 10 for separation process. At the same time, elastic member 150 retracts support member 140, feed roller 130, and drive roller 120. If elastic member 150 cannot instantaneously retract and because separation gear 114 is still causing separation rim 116 to turn, feed rim 136 will either push or pull paper 10 and cause wrinkle or tear because of the different velocity of feed rim 136 and separation rim 116. Moreover in designing the device, the dimensions of separation rim 116 and feed rim 136 have to be the accurately identical. If the dimensions differ in separation rim 116 and feed rim 136, the linear velocity of paper 10 is unequal and will easily cause paper 10 to have wrinkle or tear.
An object of the present invention is to provide to a paper collecting device suitable to use in an ADF. It can accommodate separation rims and feed rims of different sizes and still maintain the same linear velocity for the paper at contact with the separation rim and feed rim to prevent pushing or pulling of paper causing paper wrinkle and tear.
In order to achieve the above object, a paper collecting device suitable to use in an ADF comprises a separation roller, a drive roller, a feed roller, a support member, and an elastic member. In this device, besides the separation roller having a one-way clutch, another one-way clutch is added in between the feed roller and feed gear. When feeding process of the paper stops, the separation shaft immediately reverses rotation to operate other parts. This will cause the separation rim and the feed rim to release from the driving source of the motor and allow them to rotate freely at the same tangential velocity. As a result, the paper is prevented from pushing or pulling by the feed rim, which causes paper wrinkle and tear.
Furthermore, the device in this invention allows the diameter of the feed rim to be smaller than the separation rim. The tangential velocity at the points of contact of the paper and the separation rim and the feed rim should be the same. However due to the feed rim having a smaller diameter than the separation rim, the tangential velocity of the separation rim is larger than the tangential velocity of the feed rim because the gear ratio between the separation gear and the feed gear is identical so the separation gear, separation rim, and feed gear all have the same angular velocity. Therefore in order to maintain the same tangential velocity at the points of contact of the paper and the separation rim and the feed rim, the one-way clutch inside the feed roller automatically disengages to allow the feed rim to rotate freely. This maintains a same tangential velocity when the same piece of paper contact the separation rim and the feed rim during the conveyance of the paper from the feed rim to the separation rim to prevent paper being pushed or pulled causing paper wrinkle and tear.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.